Development and Validation of Mechanistic-Empirical Design Method for Permeable Interlocking Concrete Pavement

Transcription

1 Development and Validation of Mechanistic-Empirical Design Method for Permeable Interlocking Concrete Pavement Hui Li, David Jones, Rongzong Wu, and John Harvey University of California Pavement Research Center David Smith Interlocking Concrete Pavement Institute TRB 95 th Annual Meeting. Jan 10 th 14 th, 2016

2 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

3 Introduction Interest in using permeable pavements in higher traffic applications Previous work by UCPRC Preliminary Caltrans Study ( ) on permeable concrete and asphalt pavements No validation with traffic Validation study funded by industry Study objective Develop mechanistic-based design method and tables for PICP

4 Introduction Study approach Literature review Field testing Test track design Test track construction Accelerated load testing Data Analysis Design method & tool Design tables Final report includes interim reports

5 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

6 Design Method Distress Unbound layer rutting Approach Shear stress to shear strength ratio (SSR) at top of layer 0.3 SSR 0.7 Required inputs Unbound layer stiffness, strength, and other mechanical properties Obtained from lab and field testing

7 Design Subbase Thickness Subbase Thickness Shear Stress Ratio (SSR) Calculated (mm) Dry Wet As- Built Thin Medium Thick 0.2 1,350 1, Surface 80 mm interlocking concrete paver Bedding layer 50 mm ASTM #8 aggregate Base layer 100 mm ASTM #57 aggregate Subbase layer Varying thickness ASTM #2 aggregate Subgrade soil Silty clay, compacted after excavation

8 Design

9 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

10 UCPRC Facility

11 Test Track Construction

12 Test Track Construction

13 Instrumentation Aggregate size limited options Stress (pressure cell) Top of base Top of subgrade Deformation (profiler + dipsticks) Surface Top of base Top of subgrade Deflection (RSD) Water level Manual and automated

14 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

15 APT Test Program Extended HVS (13m) used to test all sub sections together Bidirectional trafficking with wander Wheel load range from 25kN to 80kN Three testing conditions Dry Wet: water table maintained at the top of the subbase Drained: Wet subgrade, no water in the subbase All testing at ambient temperature Failure criteria >25 mm of surface rut

16 APT Wet Testing

17 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

18 APT Visual Assessment

19 Average Total Rut (mm) Average Total Rut (mm) APT Total Surface Rut mm 650 mm 950 mm 25kN 40kN 60kN Load Repetitions (x 1,000) Wet Dry 450 mm 650 mm 950 mm 25kN 40kN 60kN 80kN Load Repetitions (x 1,000)

20 Permanent Deformation (mm) Permanent Deformation (mm) APT Down Rut: 450mm Subbase Top of Subbase Top of Subgrade Total Deformation 25kN 40kN 60kN Load Repetitions (x 1,000) Wet Dry Top of Subbase Top of Subgrade Total Deformation 25kN 40kN 60kN 80kN Load Repetitions (x 1,000) Bedding & Base Subbase Subgrade

21 Permanet Deformation (mm) Permanent Deformation (mm) APT Down Rut: 950mm Subbase Top of Subbase Top of Subgrade Total Deformation 25kN 40kN 60kN Load Repetitions (x 1,000) Dry Wet Top of Subbase Top of Subgrade Total Deformation 25kN 40kN 60kN 80kN Load Repetitions (x 1,000) Subbase Subgrade

22 APT General Observations Significant difference in wet and dry testing Wet test rutting was in both subbase and subgrade Thickness design to prevent rutting in subgrade Subbase aggregate properties and construction quality are critical to minimize subbase rutting

23 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

24 M-E Design Procedure Design procedure and parameters adjusted from initial design based on actual test track values Rut models developed for each layer Partial validation of rut models using APT data Analyzed with OpenPave software Design tool developed (Excel spreadsheet) Number of days with water in the subbase Material properties Traffic and load spectra Tool used to validate ICPI design tables Less conservative than current ICPI for dry conditions Slightly more conservative for very wet conditions

25 Rut Models for Different Layers

26 Input Parameters for M-E Design

27 Rut Depth (mm) Validation of M-E Design Method Dry_Measured Dry_Calculated Allowable Rut Depth Wet_Measured Wet_Calculated ,000 Subbase Thickness (mm)

28 M-E Design Tool for PICP Structure & Materials Climate Layer Moisture Condition Thickness (mm) Stiffness (MPa) 1 Poisson's Ratio c (kpa) φ ( ) Surface (80 mm concrete paver plus 50 mm #8 bedding and 100 mm #57 base) Wet Dry Subbase (ASTM #2) Wet Dry Subgrade (Clay) Wet Dry Number of Days in a Year When the 1. The wet stiffness to dry stiffness ratio can be assumed as 0.8, 0.6 and 0.6 for surface, subbase and subgrade layers, respectively. Subbase has Standing Water (Wet 2. Seasons when the subbase has standing water. Days) 2 20 PICP Design Tool 150 Input Traffic Traffic Volume Calculation Axle Type Wet Season 2 Dry Season Total ESALs AADT (two-way) ,538 1, ,823 2, Percent Trucks, T ,756 2, % ,095 2, Direction Distribution Factor, D ,528 1, ,324 1, Single Lane Distribution Factor, L ,481 1, ,137 1,203 1,203 Annual Growth Rate, r % Design Life (years), Y Traffic Days (days/year), TD ,738 2, Traffic Safety Factor, TSF ,201 3, ,118 2, Truck Traffic Volume, V ,617 1, Tandem 50, ,824 1,930 1,221 V = AADT T D L (1 + r ) Y/2 Y TD TSF Axle Load (kn) Axle-Load Distribution (%) Lifetime Repetition ,950 2,063 2, , Lifetime ESALs (Millions) 0.01 Outcome Rut Depth Subbase (ASTM #2) Subgrade (Clay) Layer Moisture Condition Shift Factor Surface (80 mm concrete paver plus 50 mm #8 bedding and 100 mm #57 base) Rut Depth by Layer (mm) Wet Dry Wet Dry Wet Dry Expected Total Rut Depth (mm) 23.0 Allowable Rut Depth (mm) 25.0 Satisfactory? Y Calculate Rut Depth Design Subbase Thickness

29 Example Design Tables

30 Outline Introduction Test Track Design Test Track Construction Accelerated Load Testing Test Results M-E Design Procedure Conclusions

31 Conclusions Shear stress to shear strength ratio (SSR) approach is appropriate for permeable pavement design Subgrade rutting dependent on subbase thickness Design for wet conditions Subbase thickness does not prevent subbase rutting Rutting depends on aggregate properties and construction quality Pervious concrete subbase below aggregate subbase can be considered to compensate for this Mechanistic-Empirical design tool and revised design catalogue has been developed and partially validated.

32 Thank-you